GO ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



well known to the few astronomers who are sufficiently in- 

 terested in this subject to institute observations upon these 

 objects. To Argelander, Schmidt, and Schonfeld is due the 

 greater part of the credit of having advanced our knowledge 

 of the variability of the brightness of stars to its present de- 

 gree of precision. It seems to be unfortunate that so very 

 few astronomers occupy themselves with this portion of ob- 

 servational astronomy, the neglect of which, in fact, seems 

 entirely unjustifiable. The conclusions in reference to the 

 physical condition of the stars that may be attained by ob- 

 servations of the variable stars are so related to those deriv- 

 able from the analysis of their light made by means of the 

 spectroscope that it is surprising that the older sister of these 

 two branches of observation is, in these later times, so much 

 neglected. Vierteljahrsschrift der Astron. Gesellschaft, X., 74. 



TIME ARRANGEMENT AT PITTSBURGH. 



In his account of the very perfect arrangements at Pitts- 

 burgh for the regulation of the city time, Professor Langley 

 states that, by the discrepancies of clocks and watches, the 

 amount of time wasted is in the aggregate very considerable, 

 and is indirectly felt by every individual, making it a public 

 convenience to have a simple and universally accessible means 

 of obtaining standard time throughout the community. The 

 arrangements devised by him for doing this are in some de- 

 gree peculiar to Pittsburgh, which is as yet in advance of all 

 other American cities in this respect. The astronomers at 

 the Observatory in Allegheny City having accurate time for 

 conducting their observations, it was only necessary to se- 

 cure some means by which this time could be reliably and 

 widely distributed. Electricity was called in to do this, a 

 current being automatically sent from the observatory clock 

 to the large tower clock in the City Hall at every beat of 

 the seconds pendulum, and by an electro-magnetic arrange- 

 ment in the turret that clock is caused to beat in perfect 

 unison with the standard at the observatory; it also auto- 

 matically gives notice to the observatory if it is in error to 

 any extent. At the exact second of noon a special current 

 is sent, which raises a detent, and allows a hammer to strike 

 the large bell at the proper instant. The public appreciation 

 of the convenience and utility of the system is daily shown 



